1. Field of the Invention
The present application generally relates to medical prostheses, methods for fabricating the prostheses, and methods for treating diseased or damaged tissue. More specifically, the present application relates to treatment of blood vessels or other body lumens and body cavities, including aneurysms such as in the aorta or in the brain.
An aneurysm is the localized dilation of a blood vessel which presents a serious medical condition. Such distention is the result of localized weakening of the vessel often caused by atherosclerosis, infection, or congenital defects. Most commonly aneurysms occur in arteries at the base of the brain or in the aorta. Cases of significant distention risk the possibility of vessel rupture and the resulting internal hemorrhage is a life threatening medical emergency that requires immediate surgical intervention. Aneurysms that are large enough to present an unacceptable level of risk of rupture are treated with preemptive surgery.
The most reliable surgical remedy for aneurysms is excision of the aneurysm and repair of the afflicted blood vessel with a graft. However, this procedure requires highly invasive surgery and often requires clamping of a major vessel such as the aorta, which can place a large strain on the patient's heart. Patients requiring aneurysm treatment often have co-morbid risk factors such as diabetes, heart disease, and hypertension, and thus such patients can be poor candidates for such a stressful operation. Accordingly, newer endovascular grafting methods for minimally invasive intervention of aneurysms are favored over traditional grafts for some patients. These endovascular installed grafts or “endoluminal grafts” are installed by accessing the aneurysm through the femoral arteries and have stent-like scaffolding supports at its terminal ends. Endoluminal grafts, however, in some situations are more prone to post-operative complications than traditionally installed grafts. Within two years of installation, a significant number of aortic endoluminal grafts exhibit leakage at the proximal interface to the aorta, necessitating further endovascular surgical intervention. Additionally, a small portion of endoluminal grafts drift inside the repaired blood vessel and expose the aneurysm. Repair of a drifted graft requires open surgery in a patient who is likely a poor candidate for such a procedure.
Endoluminal grafting must overcome geometrical problems stemming from morphological variations in aneurysm presentation and location. While most aneurysms are “fusiform,” exhibiting distention along the entire circumference of the afflicted blood vessel, varied geometries exist. Some aneurysms display ballooning of the vessel on one side at a narrow neck (also referred to as saccular), or may have otherwise treacherous geometries. Other aneurysms may be located in close proximity to sensitive structures such as renal arteries. Endoluminal grafts in certain situations may encounter higher incidence of failure with non-fusiform geometries and may be unsuitable for implantation where the implants and their delivery techniques prove too incompatible or cumbersome for aneurysm geometry or location.
Since the introduction of the stent graft in 1992, there is a persistent problem of endoleaks. The purpose of the placement of the stent graft is to direct the blood flow through the lumen of the stent graft and isolate the aneurysm sac. Clinical success is determined by the complete exclusion of the sac. However, in more than 20% of the cases, the aneurysm sac is not effectively excluded whereby blood ‘leaks’ in to the sac. This leak is defined as ‘endoleak’. The result is the sac continues to grow due to the persistent pressure of the blood against a weakened blood vessel wall, the risk of the blood vessel wall rupture is not mitigated, and the treatment is deemed to be a failure. Endoleak is a major cause of complication, and the post-operative management of the endoleaks is cumbersome and messy.
There are actually five kinds of endoleaks associated with the currently marketed stent grafts. Type I endoleak refers to the leakage of the blood flow into the sac because of an incomplete seal at the ends of the stent graft. Type II endoleak occurs when blood flows into the sac from the side branches in a retrograde fashion. Type III endoleak is defined when there is an ineffective seal at the joints of two limbs of the stent graft. Type IV endoleak happens in there is a defect, such as porosity in the graft material. Finally, Type V endoleak, known as endotension, is not really a leak, but a persistence of blood pressure in the aneurysm sac which continues to enlarge the sac towards eventual rupture if left untreated.
The most persistent endoleak is Type II where the blood comes into the aneurysm pocket from the side branches. The current therapy is to block the side branches from having any flow outward or inward. Preferred embodiments of the current invention may provide a more effective method of achieving the same.
Given these concerns, there is strong unmet need for improved endoluminal grafts and delivery methods. Such an improved design preferably facilitates more reliable repair of aneurysms over a wider space of geometries and the ability to be delivered with such finesse as to shorten procedure time and expand the number of aneurysms that are treatable endovascularly. It would also be desirable if such improved endoluminal grafts also fit the patient's anatomy more accurately and therefore help prevent endoleaks and more securely anchor the endograft in the aneurysm and prevent drifting. At least some of these objectives will be met by the devices described herein.
2. Description of Background Art
Patents and Publications related to personalizable implants include but are not limited to U.S. Pat. Nos. 8,945,199; 8,926,682; 8,906,084; 8,870,941; 7,951,448; 7,799,047; 7,790,273; 7,769,603; 7,666,220; 7,530,988; 7,483,558; 7,201,762; 7,029,487; 6,695,833; 6,500,190; 6,165,193; 4,436,684; and U.S. Patent Publication Nos. 2011/0016690; 2008/0228216; 2008/0039923; and 2006/0058638.